Billionaire Barry Diller’s Aereo is broadening availability of its service even as broadcasters challenge the legality of the startup’s live television transmissions over the Internet.

Aereo is still limited to residents of New York City, but it’s now available on additional devices including Windows computers and on a wider selection of Web browsers including Chrome, Firefox and Internet Explorer. Before, access was restricted to selected Apple devices such as the iPhone and the iPad, as well as the Roku streaming set-top box.

The company says it doesn’t expect to announce additional cities for a few more months. It also says the service isn’t likely to be available on Android devices until late this year.

Aereo lets customers capture over-the-air broadcasts from 29 local channels for viewing on devices, with subscriptions starting at $8 a month. Aereo has created a dime-sized TV antenna and crams hundreds and perhaps thousands of them into dishwasher-size boxes located at the company’s offices in Brooklyn. A customer who watches or records a show is temporarily assigned an antenna, which picks up the show and streams it over the Internet.

A copyright infringement lawsuit filed by Fox, ABC, CBS, NBC and others accuses Aereo of unlawfully copying their programming and retransmitting over the Internet. Aereo insists what it’s doing is legal because customers are assigned individual antennas. Therefore, the company says, it’s similar to what viewers would get for free by installing the same equipment at home. By contrast, cable TV companies use one antenna — or arrange a single direct feed from a broadcaster — to pick up a station for thousands of subscribers.

In July, a federal judge in New York refused to give broadcasters a preliminary injunction to stop the service, though the case remains pending.

Aereo has more than $25 million in venture capital backing, with more than $20 million of it coming from a funding round led by Diller’s IAC/InterActiveCorp, which owns Match.com, Ask.com and other websites.